What is the recommended use and dosage of Hydralazine (hydralazine) for treating hypertension?

From the Guidelines

Hydralazine is recommended for treating hypertension, typically as an add-on medication when first-line agents are insufficient, with a usual starting oral dose of 10 mg four times daily for the first 2-4 days, then increasing to 25 mg four times daily for the remainder of the first week, and a maximum daily dose of 300 mg. For adults with hypertension, the dose can be gradually increased to 50 mg four times daily in the second week if needed. Most patients require 100-200 mg daily divided into four doses. For hypertensive emergencies, hydralazine can be administered intravenously at 10-20 mg doses or intramuscularly at 20-40 mg doses, repeated as necessary, as stated in the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1.

Key Considerations

• Hydralazine works by directly relaxing vascular smooth muscle, primarily in arterioles, leading to decreased peripheral resistance and blood pressure reduction.
• Common side effects include headache, palpitations, and tachycardia due to reflex sympathetic activation.
• Long-term use requires monitoring for potential development of drug-induced lupus syndrome, particularly in slow acetylators.
• Hydralazine is often combined with a beta-blocker to counteract reflex tachycardia and with a diuretic to enhance its antihypertensive effect and reduce fluid retention, as suggested in the resistant hypertension: detection, evaluation, and management: a scientific statement from the American Heart Association 1.
• The addition of hydralazine should be considered and combined with nitrates in cases of heart failure, with total daily doses of hydralazine being <150 mg to avoid drug-induced systemic lupus erythematosus, as recommended in the same scientific statement 1.
• Hydralazine can be administered at a dose of 25 mg three times daily and titrated upward to max dose, with patients with congestive heart failure with reduced ejection fraction requiring background isosorbide mononitrate 30 mg daily, as stated in the resistant hypertension management guidelines 1.

Dosage and Administration

• The usual starting oral dose is 10 mg four times daily for the first 2-4 days.
• The dose can be gradually increased to 25 mg four times daily for the remainder of the first week.
• The dose can be further increased to 50 mg four times daily in the second week if needed.
• Most patients require 100-200 mg daily divided into four doses.
• The maximum daily dose is 300 mg.
• For hypertensive emergencies, hydralazine can be administered intravenously at 10-20 mg doses or intramuscularly at 20-40 mg doses, repeated as necessary.

From the FDA Drug Label

Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. For the second and subsequent weeks, increase dosage to 50 mg four times daily. For maintenance, adjust dosage to the lowest effective levels. In a few resistant patients, up to 300 mg of hydrALAZINE hydrochloride tablets daily may be required for a significant antihypertensive effect.

The recommended use and dosage of Hydralazine for treating hypertension is to initiate therapy with 10 mg four times daily, increasing to 25 mg four times daily after 2-4 days, and then to 50 mg four times daily after one week. The maintenance dosage should be adjusted to the lowest effective level, with a maximum of 300 mg daily in resistant patients 2.

• Initial dosage: 10 mg four times daily
• Dosage increase: 25 mg four times daily after 2-4 days, and 50 mg four times daily after one week
• Maximum dosage: 300 mg daily in resistant patients
• Key consideration: Adjust dosage to the lowest effective level to minimize the risk of toxic reactions.

From the Research

Recommended Use of Hydralazine

• Hydralazine is a direct-acting vasodilator used for the treatment of hypertension since the 1950s 3
• It is still widely used in developing countries due to its lower cost, although it has largely been replaced by newer antihypertensive drugs with more acceptable tolerability profiles 3

Dosage of Hydralazine

• The optimal dosage of hydralazine for treating hypertension is not well established, as there is insufficient evidence to conclude on its effects versus placebo on mortality, morbidity, withdrawals due to adverse effects, serious adverse events, or systolic and diastolic blood pressure 3
• A study found that the mean dose of intravenous hydralazine used in a university teaching hospital was 11.4 ± 4.3 mg, with a total of 201 doses administered to 94 patients 4

Adverse Effects of Hydralazine

• Some of the adverse effects related to hydralazine that have been reported in the literature include reflex tachycardia, hemolytic anemia, vasculitis, glomerulonephritis, and a lupus-like syndrome 3
• A study found that 17 patients experienced an adverse event after receiving intravenous hydralazine, the most common being hypotension (n = 11) 4

Use of Hydralazine in Specific Patient Populations

• Hydralazine has been widely used in the treatment of hypertension in eclampsia and preeclampsia, and its safety has been demonstrated in these patients 5
• A study found that as-needed oral hydralazine is frequently prescribed for acute blood pressure lowering in hospitalized medicine patients, with administration thresholds often less than what are used to define acute severe hypertension 6